The invention relates to a steam turbine and in particular to a design for a turbine wheel that is operable with contaminated steam. Steam turbines are generally constructed with multistage fans each having precision fabricated fan blades. The high initial cost of fabricating the precision blades restricts the driving medium to one that is non-corrosive, either chemically or mechanically. In this manner, maintenance and replacement is minimized in order that the high initial cost can be returned.
In certain circumstances, however, it is a worthwhile tradeoff to exchange the highly efficient blade turbine for a less efficient alternative turbine if an otherwise undesirable power source can be utilized. For example, in tapping natural geothermal steam sources, the steam is often contaminated with sulphur compositions which generate sulphuric acid and other corrosive compounds. Similarly, in tapping the heat source of molten rock in volcanic flues or the magma below the earth's crust by the forced introduction of water where a closed heat exchange system is not utilized, the steam generated is contaminated by corrosives. Again a turbine system for production of mechanical or electrical that can withstand the corrosive effect of the steam is necessary.
Even in engine systems where combustion products of conventional fuels mixed with steam generated from the injection of water, the resultant gas mixture is more corrosive than either the combusted gases or steam alone, thus requiring other than conventional fan-type turbines.
In such situations, a turbine that is designed to withstand corrosive, contaminated steam, and is designed for easy replacement of the elements defining the nozzle passages is desired. The bucket-less turbine wheel of this invention is devised for utilization of a contaminated drive medium.